Stereochemistry

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Stereochemistr y Isomer Organization Isomers Stereoisomer s Enantiomer s Geometric Cis/trans Cis/trans Constitutional isomers Diastereomers Conformationa l Isomers Meso compounds Epimers Stereoisomers • Same bonding sequence. • Different arrangement in space. • Example: HOOC-CH=CH-COOH has two geometric (cis-trans) isomers O H HO C C C C OH H O fumaric acid, mp 287o  C   essential metabolite O HO C H O C C C OH H => maleic acid, mp 138o  C      toxic irritant Chirality • “Handedness”: right glove doesn’t fit the left hand. • Mirror-image object is different from the original object Examples of Handed Objects • • • • • Your hands, from the previous slide Gloves Scissors Screws Golf clubs How about molecules? • Chemical substances can be handed • Handed substances are said to be chiral • Molecules, that are chiral are nonsuperimposable on their mirror image Chirality in Molecules • cis isomers are achiral (not chiral). Chirality in Molecules • The cis isomer is achiral. • The trans isomer is chiral. Chirality in Molecules • The cis isomer is achiral. • The trans isomer is chiral. • Enantiomers: nonsuperimposable mirror images, different molecules. Chirality in Molecules • The cis isomer is achiral. • The trans isomer is chiral. • Enantiomers: nonsuperimposable mirror images, different molecules. • One enantiomeric form of limonene smells like oranges, while its mirror image smells like lemons.
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